BMW M4 - a car dominated by its engine - PH Fleet

[brava09]

http://www.pistonheads.com/regulars/...ph-fleet/32941



4.1 seconds. That's how long 'my' DCT-equipped BMW M4 should take to reach 62mph. On the runway of RAF Alconbury, previous occupants the US Air Force, it felt more like four minutes. Four very spectacular minutes, granted, with what little remains of the rear Michelin Pilot Sports vapourised into smoke or left in thick black lines on the abrasive concrete. More smoke than igniting the near £700 of notes the BMW dealer would want for two rears? Possibly. I had plenty of time to reflect on this as my rivals in the PH/Autocar drag race extravaganza repeatedly disappeared into the distance anyway.


What does this prove, other than I am rubbish at standing starts and now absolutely, definitely need new rear tyres for the M4? I'm more into corners than straight lines to be honest but it was quite a revealing exercise in terms of how hard it is to balance the power delivery of the turbo'd straight-six, be that in a straight line or with the car sideways.

There is a launch control function on the car but even then it was lighting up the rear tyres and leaving black lines for a good 20 metres before the electronics supposedly governing the tyre slip managed to get a grip on the situation. It seems a little fussy about when and how often it'll let you use it though, meaning for many of the runs I was on my own.

Won't win drag races, will win drift offsWon't win drag races, will win drift offs
As has been (much) discussed all M's laudable attempts to build an engine that disguises the supposed downsides of forced induction has created a motor of considerable complexity. The two small turbos spool up so fast and boost so savagely that breaking traction is all too easy - peak torque at 1,850rpm will do that. It takes real subtlety and a right foot more delicate than mine to find that narrow sweet spot between all or nothing that gives you the best of the engine without bonfiring the tyres. But once the boost is on you've got peak torque until 5,500rpm and a lovely linear spread to play with. You've just got to manage that initial jolt.

In a straight line race it's a nightmare though. Too much too soon and you spin up. Back out and try modulating the throttle back in and - boom - soon as the boost comes back you're spinning the wheels again. Short shifting helps the initial traction but then - wham - the boost comes in even more violently.

More to follow on this soon...More to follow on this soon...
Ach, it's all a bit meaningless really because who drives their personal car like this? And having to learn an engine's character is the kind of challenge I like. It's anything but dull and there are sublime moments in this car when you successfully manage that initial spike, ride out that huge mid range and just hold the car on the cusp of breaking traction out of a roundabout or corner with the active diff and stability control giving you just a hint of slide. I return to my pet hate of the fake noise but it would be a lot easier to understand what the engine is up to if you were getting real sound directly proportional to throttle opening and load. It's so frustrating because it sounds brilliant from the outside.

There are advantages to that new engine compared with its predecessor though. Regular long-haul travel down the M1 with a bit of A5 and A43 to liven up the middle before M40/M25 and suburban schlep will see it return around 30mpg which is, I think, reasonable given the state of tune. And sci-fi to those with experience of the old V8.


Rightly this is a car dominated by its engine though, and it's one I'm still learning how to make the most of. It's a fascinating process and full of reward; long-term tests are about discovering the hidden depths launch drives or regular loans don't reveal. Moreover, even though I've had a bit of a purple patch of bookings recently, hopping between some very special cars, I always feel a little spark of excitement as I unlock the M4 and leave the door open to hear that fierce cold-start bark. Small but important signs of emotional bonding an M product like this should inspire. It's not a perfect car. But it's one growing in my affections with every passing week and reveals more of itself over time.

How does it compare with the C63 you're wondering? More on that in due course... First, those tyres. And, no, I'm not going to be paying dealer prices.

[dmk08]

I just don't have the insane traction issues others speak about. Is this because I have 6MT without the DCT torque multiplication or whatever? I have upgraded my rear tires to 295 MPSS but I also have about 70tq more than stock.

[Damasconian]

More and more you see the long-term tests coming back with the same general theme:

The car is not easy to drive but the more I drive it, the more I like it.

[myzmak]

Originally Posted by dmk08

I just don't have the insane traction issues others speak about. Is this because I have 6MT without the DCT torque multiplication or whatever? I have upgraded my rear tires to 295 MPSS but I also have about 70tq more than stock.

Likewise. I have zero traction problems with the MT.

[Damasconian]

Originally Posted by dmk08

I just don't have the insane traction issues others speak about. Is this because I have 6MT without the DCT torque multiplication or whatever? I have upgraded my rear tires to 295 MPSS but I also have about 70tq more than stock.

This is the easiest car I have ever done burnouts in. Not even close really. I think the traction issues are real, but can be dealt with through many ways. Wider tires, more seat time in the car, transmission choices, etc.

I've learned a lot in the year I have owned it. That is what you would call a rewarding experience.

[CanAutM3]

Originally Posted by dmk08

I just don't have the insane traction issues others speak about. Is this because I have 6MT without the DCT torque multiplication or whatever? I have upgraded my rear tires to 295 MPSS but I also have about 70tq more than stock.

Originally Posted by myzmak

Likewise. I have zero traction problems with the MT.

DCT has 17% more torque multiplication in 1st gear than the 6MT and 12% more in 2nd. So yes, traction is more of an issue on DCT cars.

I have been griping about those stupid short DCT low gears for a while (even before I ordered my car). BMW went cheap, and just gave us a "hand-me-down" gearbox from the M5/6 instead of having one developed specifically for the F8X.

[brava09]

I had plenty of time to reflect on this as my rivals in the PH/Autocar drag race extravaganza repeatedly disappeared into the distance anyway.

That's something that would piss me off big time.

[dmk08]

Originally Posted by CanAutM3

DCT has 17% more torque multiplication in 1st gear than the 6MT and 12% more in 2nd. So yes, traction is more of an issue on DCT cars.

I have been griping about those stupid short DCT low gears for a while (even before I ordered my car). BMW went cheap, and just gave us a "hand-me-down" gearbox from the M5/6 instead of having one developed specifically for the F8X.

Ahh.. Cause my experience with 6MT, JB4 map2, downpipes, and intake are not that bad. If I am in 2nd gear around 3500 RPM I can lay into it, sure I get a little fishtail, but mostly my car just takes off like a scalded dog. Another small chrip on a hard 3rd shift but then once again it just takes off.

6MT FTW? j/k

[evanevery]

Maybe if he had real "Tires" on his car instead of "Tyres" he wouldn't have had such a problem getting a good launch...

[JoeFromPA]

Dmk,

In my 6mt, I feel traction is a real issue with the power delivery of this engine. Mostly this is observed through DSC intervention in MDM mode (which is how I drive it all the time).

One of the interesting things to me is that even though torque delivery is perceived as immediate by my brain, that is not how the tires react. The tires very much react as if this is a traditional turbocharged car where the torque comes on in a non-linear fashion and overwhelms the tires more easily than an equivalently-powered-NA-motor would. And, of course, we have more torque available at lower rolling speeds and lower RPMs in a given gear than a traditional N/A motor of similar output would provide.

I don't think this is some nightmare vehicle to manage, but I'm surprised by just how much grip has been something I observe every single day as lacking. I came from a e39 m5 and I knew the f80 m3 would have:

- More torque
- Shorter gearing
- 500 pounds less mass
- Equivalent rear tire (albeit with a customized PSS)
- A more sophisticated diff

Despite these things, I truly feel the stock f80 is on the edge of where I find RWD to be a less desirable drivetrain in how I drive compared to AWD.

That being said: I always wanted to be in a position where "too much power" was just enough And now I am. I don't yearn for more power - at all. I yearn for more traction.

[solstice]

Good article with some serious and deserved praise of the F8X that often go missing in other pieces. One of the best aspects of an M car and what sets it apart from the non Ms is that it has so much depth that you never really get bored with it. The F8X definitely ran a larger risk due to being FI with easy accessible low end power and a lower redline. However the beastly nature created by not doing torque management creates a welcome challenge and a very fun engine, couple that with the good response for an FI engine and decently linear feel to the redline and well, you have a worthy M engine.

Thanks for sharing this, very insightful for non F8X owners. Personally I seldom stab the throttle in low gears and never really had much traction issues, wet or dry. Thought it way overblown but I came to realize that many do treat the throttle as a flip switch

[Matt_B]

Originally Posted by evanevery

Maybe if he had real "Tires" on his car instead of "Tyres" he wouldn't have had such a problem getting a good launch...

Tyre is the correct spelling in much of the English speaking world, including the UK where the author is from.

[CSanto]

Originally Posted by dmk08

I just don't have the insane traction issues others speak about. Is this because I have 6MT without the DCT torque multiplication or whatever? I have upgraded my rear tires to 295 MPSS but I also have about 70tq more than stock.

+1 0 issues with traction. I can drive hard in a straight line and not have to worry about losing grip. Even my buddy with an F83 was telling me to be careful with traction when I first got the car. He has DCT. I never got the impression it was out of wack or the TC light was flashing when it shouldnt be.

[Damasconian]

Originally Posted by Matt_B

Tyre is the correct spelling in much of the English speaking world, including the UK where the author is from.

Surely he knew that and was just joking.

True story: I tried to manoeuvre my aluminium automobile away from the kerb but ended up writing a cheque for the damages.

EDIT: Should've used "Saloon" to replace "automobile" there. Missed opportunity I guess.

[AM4ZING]

Originally Posted by dmk08

Ahh.. Cause my experience with 6MT, JB4 map2, downpipes, and intake are not that bad. If I am in 2nd gear around 3500 RPM I can lay into it, sure I get a little fishtail, but mostly my car just takes off like a scalded dog. Another small chrip on a hard 3rd shift but then once again it just takes off.

6MT FTW? j/k

6MT ftw haha

With the Jb4, my car will do a 2nd gear burnout for about 2 blocks if i were to stay on it lol

[evanevery]

Originally Posted by Matt_B

Tyre is the correct spelling in much of the English speaking world, including the UK where the author is from.

What would you expect from a country that also drives on the wrong side of the road?

(Its a joke - Please disable your sarcasm filter)

[dmk08]

Originally Posted by AM4ZING

6MT ftw haha

With the Jb4, my car will do a 2nd gear burnout for about 2 blocks if i were to stay on it lol

Stock tires? I have a suspicion that normal MPSS grip better than the 'BMW SPEC' ones in general. I guess going up to 295 w/ 11" rears helped too but we are only talking 20mm.

[AM4ZING]

Originally Posted by dmk08

Stock tires? I have a suspicion that normal MPSS grip better than the 'BMW SPEC' ones in general. I guess going up to 295 w/ 11" rears helped too but we are only talking 20mm.

Stock PSS is like driving on water lol

I run 295/30r20 Pirelli Pzero. They only start gripping once warmed up completely

[rivesc]

I own a 6MT and have not really had any issues with traction yet. Granted, I just had my 1200 mile service done last week and will be pushing her a bit harder, so we'll see.

[solstice]

I would only call it traction issues if the F8X was significantly slower than other 425 hp cars of similar type. I don't see that at all indicating that the car is able put down power really well. That you can spin tires on will is not traction issues IMO it's throttle control issues

[Brosef]

Originally Posted by JoeFromPA

Dmk,

That being said: I always wanted to be in a position where "too much power" was just enough And now I am. I don't yearn for more power - at all. I yearn for more traction.

totally agreed. I think this car is finally at the point where I'm not yearning for more power. BMW gave us enough juice out of the box to max out the chassis. and I'm coming from a supercharged e92, which was a beast and a ton of fun.

Originally Posted by AM4ZING

Stock PSS is like driving on water lol

I run 295/30r20 Pirelli Pzero. They only start gripping once warmed up completely

this is the truth. the difference between warm and cold tires is significant. it takes at least one good tire spinning before you really get enough heat in the tires to make them hook up nicely.

[CanAutM3]

Originally Posted by JoeFromPA

In my 6mt, I feel traction is a real issue with the power delivery of this engine. Mostly this is observed through DSC intervention in MDM mode (which is how I drive it all the time).

I have debated this point in the past. DSC intervention should not be confused with loss of traction. Modern stability systems are predictive, not only reactive. They anticipate loss of traction and in the interest of safety, can intervene before it occurs.

The thing is, due to tire dynamics, there is a huge gray zone between grip and no grip. Tires are constantly slipping. Even a tire that has a large slip angle is still providing a certain amount of grip. Stability systems are designed to monitor the level slip and react based on either a change of slip or a difference of slip between individual wheels. That is how they can intervene before an actual loss of traction occurres.

Try DSC off. You'll find that the car has much more traction than DSC/MDM will lead you to believe.